[Methylation of the GSTP1 gene promoter in colorectal cancer]

ABSTRACT

Transcriptional silencing of tumor suppressor genes and tumor related genes like GSTP1 by methylation of promotor region CpG island is believed to be an important mechanism in tumorigenesis. The GSTP1 gene encodes the enzyme glutathione S-transferase Pi which defends the cells against oxidative damage and electrophilic carcinogens. To gain insight into the role of epigenetic silencing of GSTP1 in colorectal cancer, its methylation was investigated in the blood samples obtained from tumor tissues [n=37] and the adjacent normal tissues [n=29] of patients with colorectal cancer as well as the blood samples taken from control subjects [n=42] by PCR after using methylation - sensitive restriction endonuclease ACCI. Methylation of GSTP1 was detected in the blood samples of control and blood, adjacent normal tissue and tumor tissue groups at 9.52%, 10.81%, 17.24% and 62.1% in respectively. There was a significant association between mehtylation of the GSTP1 in tumor tissues and the risk of colorectal cancer compared to adjacent normal tissues [OR= 7.86; 95% CI= 2.316 - 26.633]. The difference between methylation of the GSTP1 in the blood samples of case and control group [OR= 1.121; 95% CI= [0.26 - 4.84] was not statistically significant. Our findings indicate that methylation of the GSTP1 promotor may be detected in the tumor tissues. This could serve as a molecular diagnosis tool in detection and treatment of colorectal cancer